The invention relates to a spreader for spreading a fluid, such as an adhesive, in a thin layer on a surface, said spreader comprising an oblong spreader housing and a plurality of outlet nozzles which are arranged at regular intervals along one side of the spreader housing, and which are connected to a feeding channel system accommodated in the housing and in turn connected to an inlet opening for said fluid.
It is known to apply adhesive onto a large surface through a number of nozzles in a spray spreader. The adhesive in question is pumped from a suitable source to a coupling device through a conduit, said conduit or conduits (used in connection with a two-component adhesive) being connected to the spreader. The known spreader comprises often a pipe or bar-like member of a length rendering it possible to coat the surface in question with the adhesive layer in question by way of a single relative movement of said surface past the spreader. Therefore, the nozzles in question are arranged adjacent one another at regular intervals. Such spreaders are for instance used in connection with plants, where the plates to be coated with an adhesive layer are advanced stepwise on a conveyor belt, said plates being advanced in lengths corresponding to the length of a spreader, such as 0.5 m, in each step. Subsequently, the spreader is moved transverse to the advancing path of the conveyor belt at the same time as adhesive is fed through the nozzles of the spreader. After each transverse movement of the spreader, the plate placed on the conveyor belt is advanced yet another step. Such plants can for instance process plates of up to 3 times 6 m to be used for the production of sandwich elements. The adhesive types in question are typically high-viscous fluids requiring a high pressure, such as 20 to 180 bar, in order to be pressed through feeding conduits and nozzles. A spreader for applying adhesive onto such plates comprises a very high number of nozzles, and accordingly it is very difficult to keep such nozzles clean or to clean said nozzles after the use thereof. Often it is not possible to carry out such a cleaning process without the use of suitable solvents. Accordingly, the cleaning process is both cost-intensive and time-consuming.
The object of the present invention is to provide a spreader avoiding the necessity of a cost-intensive and time-consuming cleaning process as well as the use of separate solvents.
The above is obtained by the spreader according to the invention being characterised in that the nozzles, their feeding channel system, and the inlet opening being shaped in a separate lining detachably secured in the housing, whereby the housing comprises cavities receiving the lining and being adapted to fixedly clamp around said lining during the use of the spreader, at least one opening being provided in said housing, where the nozzles project from the interior of the housing through said opening.
When this spreader is used, nothing but the lining is replaced by a new lining when required by the nozzles or the associated feeding channel system.
The lining may particularly advantageously comprise two interconnected, substantially plate-shaped lining members with recesses provided therein to form the nozzles the feeding channel system of said nozzles as well as the inlet opening. Such plate-shaped lining members are easy to manufacture of a suitable disposable material, such as board or plastics.
The housing may according to the invention comprise two hingedly interconnected housing parts provided with means for tightening said housing parts around the lining with the result that the opening and the closing of said housing is particularly simple.
Moreover, the lining members may according to the invention be plate or sheet-extruded, vacuum-moulded plates of plastics, which are glued or welded to one another, whereby the outlet nozzles shaped in one lining member comprise outlet orifices or openings resulting from a cutting off of portions of said lining member. The resulting manufacture of the lining members is particularly easy and inexpensive.
Furthermore, the nozzles may according to the invention be shaped in a number of rows protruding from a plane of a first plate-shaped lining member in such a manner that each nozzle extends from a plane portion coinciding with the side facing the second lining member, and the feeding channel system may form a nozzle feeding chamber adjacent said nozzles, where said nozzle feeding chamber is formed by a coherent recess in the second lining member opposite said nozzles. As a result, a particularly simple feeding of the nozzles is obtained.
According to the invention the nozzle feeding chamber may particularly advantageously be formed by a small, trough-shaped recess in the second lining member, where said small trough-shaped recess extends along the row or rows of nozzles and comprises longitudinal sides, of which one longitudinal side is positioned opposite the area along one side of the row or rows of nozzles and the other longitudinal side is positioned opposite the area along the opposite side of the row or rows of nozzles, but at a predetermined distance therefrom, said latter area being positioned upstream relative to the flow direction of the fluid inside the feeding channel system, and where a comparatively larger recess is provided opposite the small trough-shaped recess at the upstream side and along the row or rows of nozzles in the first lining member comprising said nozzles, whereby a distribution chamber is formed in this portion of the feeding channel system, said distribution chamber communicating directly with the nozzle feeding chamber. The spreader is particularly suited for use in connection with an application process involving returning interruptions between the individual applications of adhesive while producing a multilayer sandwich element or when said element is to be replaced. These interruptions can last from 1 minute and up to several hours. The structure in question of the nozzles with the associated feeding chamber and distribution chamber ensures that the interruption does not involve a noticeable afterflow of the adhesive in question, which is due to the fact that the adhesive present at a level above the nozzles is not significant and that said adhesive is instead present in the distribution chamber at a level below the inlet of each nozzle. The possible interruption period in question depends, of course, on the type of adhesive in question because said type of adhesive must not, of course, be able to cure inside the interior of the nozzles during said interruption period.
According to the invention, the portion of the feeding channel system adjacent the distribution chamber may be formed substantially by one or more recesses in the first lining member housing the nozzles, whereby the afterflow of adhesive material in connection with an interruption of the application process is not additionally stimulated.
The feeding channel system may according to the invention be provided with one or more static mixers, whereby the components of the adhesive material are efficiently mixed during the flow towards the nozzles. This or these static mixer(s) may according to the invention be arranged in their respective separate tubes, whereby it is ensured that the adhesive material does not flow round said static mixers because the separate tubes associated with said mixers can be formed very accurately to fit said static mixers.
A static mixer with the associated separate tube may according to the invention be arranged in connection with the inlet opening and comprise projecting members with means for coupling the spreader to a mixer head, which in turn comprises means for connecting conduits thereto, said conduits communicating with sources with their respective components of a two-component adhesive system. As a result, a particularly simple connection is obtained between the lining and the conduit system advancing the adhesive to the spreader.
The second lining member may according to the invention be made of a resilient plastic material, and the spreader may comprise means for allowing a closing of each nozzle by pressing the second lining member towards the first lining member opposite each nozzle.